U.S. patent application number 16/318253 was filed with the patent office on 2019-08-29 for pretreating liquid for electroless plating to be used during reduction treatment, and process for producing printed wiring board.
This patent application is currently assigned to C. Uyemura & Co., Ltd.. The applicant listed for this patent is C. Uyemura & Co., Ltd.. Invention is credited to Nobuhiko NAKA, Yoshikazu SAIJO, Hisamitsu YAMAMOTO.
Application Number | 20190264329 16/318253 |
Document ID | / |
Family ID | 61162089 |
Filed Date | 2019-08-29 |
![](/patent/app/20190264329/US20190264329A1-20190829-D00001.png)
United States Patent
Application |
20190264329 |
Kind Code |
A1 |
SAIJO; Yoshikazu ; et
al. |
August 29, 2019 |
PRETREATING LIQUID FOR ELECTROLESS PLATING TO BE USED DURING
REDUCTION TREATMENT, AND PROCESS FOR PRODUCING PRINTED WIRING
BOARD
Abstract
A novel pretreating liquid for electroless plating which is used
simultaneously with reduction treatment after roughening treatment
of a filler-containing insulating resin substrate. A pretreating
liquid for electroless plating is used simultaneously with
reduction treatment when an insulating resin substrate containing a
filler is roughened and residues generated on the insulating resin
substrate are reduced. The pretreating liquid comprises: a reducing
agent; and at least one selected from the group consisting of
ethylene-based glycol ether represented by
CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1 to 4, n=an
integer of 1 to 4) and propylene-based glycol ether represented by
CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1 to 4, y=an
integer of 1 to 3).
Inventors: |
SAIJO; Yoshikazu; (Osaka,
JP) ; YAMAMOTO; Hisamitsu; (Osaka, JP) ; NAKA;
Nobuhiko; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
C. Uyemura & Co., Ltd. |
Osaka |
|
JP |
|
|
Assignee: |
C. Uyemura & Co., Ltd.
Osaka
JP
|
Family ID: |
61162089 |
Appl. No.: |
16/318253 |
Filed: |
June 19, 2017 |
PCT Filed: |
June 19, 2017 |
PCT NO: |
PCT/JP2017/022512 |
371 Date: |
January 16, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 18/38 20130101;
C11D 7/04 20130101; C23C 18/26 20130101; C23C 18/2086 20130101;
C23C 18/18 20130101; H05K 2203/072 20130101; H05K 3/182 20130101;
C23C 18/16 20130101; C11D 7/10 20130101; H05K 3/18 20130101 |
International
Class: |
C23C 18/26 20060101
C23C018/26; H05K 3/18 20060101 H05K003/18; C11D 7/10 20060101
C11D007/10; C11D 7/04 20060101 C11D007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2016 |
JP |
2016-158009 |
Claims
1. A pretreating liquid for electroless plating to be used
simultaneously with reduction treatment when an insulating resin
substrate containing a filler is roughened and residues generated
on the insulating resin substrate are reduced, the pretreating
liquid comprising: a reducing agent; and at least one selected from
the group consisting of ethylene-based glycol ether represented by
CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1 to 4, n=an
integer of 1 to 4) and propylene-based glycol ether represented by
CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1 to 4, y=an
integer of 1 to 3).
2. The pretreating liquid for electroless plating according to
claim 1, further comprising a fluorine compound.
3. The pretreating liquid for electroless plating according to
claim 1, wherein the insulating resin substrate contains a
silica-based filler, and the content of SiO.sub.2 in the insulating
resin substrate is 30% by mass or more.
4. A process for producing a printed wiring board, comprising: a
roughening treatment step of roughening an insulating resin
substrate containing a filler; a reduction and filler removal step
of reducing residues generated on the insulating resin substrate by
the roughening treatment step and, at the same time, removing the
filler contained in the resin insulating substrate; and an
electroless plating step of applying electroless plating to an
insulating resin etched in the reduction and filler removal step,
wherein in the reduction and filler removal step, a treating liquid
containing a reducing agent and at least one selected from the
group consisting of ethylene-based glycol ether represented by
CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1 to 4, n=an
integer of 1 to 4) and propylene-based glycol ether represented by
CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1 to 4, y=an
integer of 1 to 3) is used.
5. The production process according to claim 4, wherein in the
reduction and filler removal step, a treating liquid further
comprising a fluorine compound is used.
6. The production process according to claim 4, wherein the
insulating resin substrate contains a silica-based filler, and the
content of SiO.sub.2 in the insulating resin substrate is 30% by
mass or more.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pretreating liquid for
electroless plating to be used during reduction treatment in
production of a printed wiring board containing a filler in an
insulating resin, and a process for producing a printed wiring
board.
BACKGROUND ART
[0002] The printed wiring boards widely used in the electronics and
other fields usually may be often produced by applying a catalyst
to an insulating resin substrate, carrying out electroless plating
such as electroless copper plating, and if necessary, carrying out
subsequent electroplating such as electrolytic copper plating.
Since no chemical bond is formed between the insulating resin
substrate and copper, high adhesion cannot be expected between the
insulating resin substrate and a copper plating film. Thus, in the
past, there has been adopted a method in which after an insulating
resin substrate is swollen and then immersed in a roughening
solution containing an oxidizing agent such as permanganate or
chromate to roughen (etch) the surface of the insulating resin
substrate and thus to form an anchor shape, whereby the adhesion
between the insulating resin substrate and a copper plating film is
enhanced. The above-described roughening solution is also called a
desmear solution and is used to remove resin scum (smear) generated
in many holes (such as blind vias and through holes for connecting
a plurality of conductors and a trench used for forming a circuit)
provided on a printed wiring board and on the substrate surface,
along with the formation of the holes. A treatment method including
a series of processes such as the above-described swelling
treatment and roughening treatment (etching with an oxidizing
agent), reduction treatment (also called neutralization treatment)
for dissolving and removing a residue (such as manganese oxide
derived from sodium permanganate) generated on the surface of a
resin substrate by roughening treatment, and cleaning treatment
with a conditioner is called a desmear treatment method.
[0003] The insulating resin may often contain a filler such as a
silica-based filler, so that the insulating resin substrate can
have improved mechanical and electrical characteristics, and at the
same time, the anchor effect in the above-described roughening
treatment enhances the adhesion between the insulating resin
substrate and a plating film.
[0004] In recent years, there has arisen the problem of a decrease
in the adhesion to the plating film as the surface roughness
(anchor irregularities; represented by Ra) of the insulating resin
substrate becomes small with high functionalization and high
integration of printed wiring boards. In addition, as the thermal
expansion coefficient of a resin material is reduced, the content
of a filler contained in the resin material increases, and there is
a problem that sufficient adhesion with the plating film cannot be
ensured in the conventional desmear treatment.
[0005] Thus, the present applicant has disclosed, in Patent
Document 1, a reduction and removal treatment liquid containing a
reducing agent and a fluorine compound. The treatment liquid is a
pretreating liquid for electroless plating used for forming a
printed wiring board containing a filler in an insulating resin,
and used for reducing residues such as oxides generated by
roughening treatment and a reduction and removal process for
removing the filler. It has been demonstrated that when a fluorine
compound having the effect of removing a filler during reduction
treatment is thus used as a filler removal treatment agent, high
adhesion to a plating film can be obtained even with a substrate
having a small surface roughness.
PRIOR ART DOCUMENT
Patent Document
[0006] Patent Document 1: JP-A-2013-153223
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0007] The present invention has been made to provide a novel
pretreating liquid for electroless plating which is used
simultaneously with reduction treatment after roughening treatment
of a filler-containing insulating resin substrate.
Solutions to the Problems
[0008] The pretreatment liquid for electroless plating of the
present invention which could solve the above problem is as
follows.
[0009] Item 1
[0010] A pretreating liquid for electroless plating to be used
simultaneously with reduction treatment when an insulating resin
substrate containing a filler is roughened and residues generated
on the insulating resin substrate are reduced, the pretreating
liquid comprising:
[0011] a reducing agent; and
[0012] at least one selected from the group consisting of
ethylene-based glycol ether represented by
CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1 to 4, n=an
integer of 1 to 4) and propylene-based glycol ether represented by
CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1 to 4, y=an
integer of 1 to 3).
[0013] Item 2
[0014] The pretreating liquid for electroless plating according to
above item 1, further comprising a fluorine compound.
[0015] Item 3
[0016] The pretreating liquid for electroless plating according to
above item 1 or 2, wherein the insulating resin substrate contains
a silica-based filler, and the content of SiO.sub.2 in the
insulating resin substrate is 30% by mass or more.
[0017] Further, the process for producing a printed wiring board of
the present invention which could solve the above problem is as
follows.
[0018] Item 4
[0019] A process for producing a printed wiring board,
comprising:
[0020] a roughening treatment step of roughening an insulating
resin substrate containing a filler;
[0021] a reduction and filler removal step of reducing residues
generated on the insulating resin substrate by the roughening
treatment step and, at the same time, removing the filler contained
in the resin insulating substrate; and
[0022] an electroless plating step of applying electroless plating
to an insulating resin etched in the reduction and filler removal
step,
[0023] wherein in the reduction and filler removal step, a treating
liquid containing a reducing agent and at least one selected from
the group consisting of ethylene-based glycol ether represented by
CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1 to 4, n=an
integer of 1 to 4) and propylene-based glycol ether represented by
CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1 to 4, y=an
integer of 1 to 3) is used.
[0024] Item 5
[0025] The production process according to above item 4, wherein in
the reduction and filler removal step, a treating liquid further
comprising a fluorine compound is used.
[0026] Item 6
[0027] The production process according to above item 4 or 5,
wherein the insulating resin substrate contains a silica-based
filler, and the content of SiO.sub.2 in the insulating resin
substrate is 30% by mass or more.
Effect of the Invention
[0028] By using the pretreating liquid of the present invention, a
printed wiring board having excellent adhesion between the
filler-containing insulating resin substrate and the plating film
can be obtained.
[0029] According to the present invention, for example, in
consideration of production of a high-density and high-precision
printed wiring board, even if surface roughness of the
filler-containing insulating resin substrate is not roughened (that
is, even if irregularities on the surface of the filler-containing
insulating resin substrate are small), or even if the content of
the filler contained in the insulating resin is large, the adhesion
between the substrate and the plating film is remarkably improved.
Thus, the technique of the present invention is preferably used for
manufacturing a circuit board having a small surface roughness as
in a high-speed signal, high-density wiring, and the like.
[0030] Further, the technique of the present invention is applied
to not only production of a high density multilayer wiring board by
a process for producing a wiring board and a build-up construction
method, but also production of a multilayer wiring layer in a wafer
level CSP (Chip Size epoxy Package or Chip Scale epoxy Package),
TCP (Tape Carrier Package), or the like.
BRIEF DESCRIPTION OF THE DRAWING
[0031] FIG. 1 (a) is a surface SEM photograph of Test No. 19
(Comparative Example) in Table 1, and FIG. 1 (b) is a surface SEM
photograph of Test No. 5 (Working Example) in Table 1.
MODE FOR CARRYING OUT THE INVENTION
[0032] The present inventors have been under consideration in order
to provide a surface treatment method (desmear treatment) for
producing a printed wiring board having good adhesion to a plating
film even when surface roughness (Ra) of the filler-containing
insulating resin substrate is as small as about 0.01 to 0.3 pun or
the content of the filler (in terms of SiO.sub.2) contained in the
insulating resin is as much as about 30% by mass or more. As a
result, the present inventors have found that the intended purpose
is attained by using, as a treating liquid (treatment agent) to be
used simultaneously with reduction treatment (neutralization
treatment) after roughening treatment of the filler-containing
insulating resin substrate, a treating liquid containing a reducing
agent and at least one selected from the group consisting of
ethylene-based glycol ether represented by
CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1 to 4, n=an
integer of 1 to 4) and propylene-based glycol ether represented by
CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1 to 4, y=an
integer of 1 to 3), thereby completing the present invention. The
ethylene- or propylene-based glycol ether to be used in the present
invention may hereinafter be abbreviated as the glycol ether.
[0033] In the present invention, the pretreating liquid
(pretreating agent) for electroless plating to be used during
reduction treatment means a pretreating liquid used together with a
reducing agent when an insulating resin substrate containing a
filler is roughened and residues generated on the insulating resin
substrate are reduced. For example, taking a method of producing a
printed wiring board by copper plating, as an example, when an
insulating resin substrate containing a filler is subjected to
swelling treatment, roughening treatment, reduction treatment
(neutralization treatment) for reducing oxides generated in the
roughening treatment, if necessary, ultrasonic treatment, drying,
conditioning (cleaning), soft etching, pickling, catalyst
imparting, electroless copper plating, and electrolytic copper
plating to produce the printed wiring board, the pretreating liquid
is a pretreating liquid to be used simultaneously with a reducing
agent after the roughening treatment. In the present invention, the
above-described pretreating liquid for electroless plating to be
used simultaneously with reduction treatment may be abbreviated as
the pretreating liquid. Further, the filler-containing insulating
resin substrate may be referred to simply as an insulating resin
substrate or a resin substrate.
[0034] The characteristic part of the present invention is that as
a pretreating liquid to be used simultaneously with reduction
treatment (neutralization treatment), the above-described glycol
ether is used together with a commonly used reducing agent. As a
result of the investigation conducted by the present inventors,
they have found that good filler removing action is exhibited by
using the above-described glycol ether together with the reducing
agent during reduction treatment. As a result, they have found that
good adhesion can be obtained even when a filler-containing
insulating resin substrate having a small surface roughness or an
insulating resin substrate containing a large amount of filler,
which has been difficult to adhere to a plating film, is used,
thereby completing the present invention.
[0035] This point will be described in a little more detail.
Usually, when the filler-containing insulating resin substrate is
etched by roughening treatment with an oxidizing agent (such as Mn
in permanganate or the like), the oxidizing agent such as Mn is
adsorbed on the surface of the filler contained in the insulating
resin substrate and the surface of the resin holding the filler.
While the oxidizing agent such as Mn adsorbed on the surface is
dissolved by the subsequent reduction treatment
(oxidation-reduction reaction) with a reducing agent (neutralizing
agent), the filler is removed by oxygen gas generated at that time.
In the roughening treatment, although a very narrow gap (interval)
is formed between the filler reduced by etching and the resin
holding the filler, the reducing agent (neutralizing agent) used
for usual reduction treatment is inferior in permeability, and
therefore, the reducing agent hardly penetrates into the very
narrow gap. Thus, the above-described oxidation-reduction reaction
does not sufficiently proceed, and the filler is hardly
removed.
[0036] On the other hand, since the above-described glycol ether
used in the present invention is excellent in permeability, the
glycol ether penetrates into even the very narrow gap described
above. As the glycol ether penetrates into the gap (together with
the permeation of the glycol ether), a reducing agent also reaches
the gap to penetrate into the gap and thus to enter the gap,
whereby the reducing agent reacts with an oxidizing agent such as
Mn to generate oxygen gas. It is considered that the filler is
extruded and removed by the oxygen gas, and as a result, adhesion
between a resin substrate and a plating film is remarkably
improved.
[0037] That is, the glycol ether used in the present invention
exhibits a good filler removing effect by being used in combination
with a reducing agent and has an effect of contributing to
improvement in adhesion to the plating film.
[0038] As described above, in the present invention, an insulating
resin substrate which has been swollen is roughened using potassium
permanganate or the like, and then, while the pretreating liquid of
the present invention is applied, the filler is removed during
dissolution and removal according to reduction reaction of
treatment residues generated by the roughening treatment. This is
because even if the filler is to be removed before the roughening
treatment using potassium permanganate or the like, the filler is
contained in the resin so as to be covered with the resin, and
therefore, the filler cannot be removed effectively, so that a
sufficient adhesion improvement effect between the insulating resin
substrate and the plating film cannot be exhibited. Thus, in the
present invention, the resin covering the filler is first removed
by roughening the resin substrate, and then the filler is removed
during removal of residues such as oxides generated by the
roughening treatment.
[0039] The pretreating liquid for electroless plating of the
present invention contains a reducing agent and at least one
selected from the group consisting of ethylene-based glycol ether
represented by CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1
to 4, n=an integer of 1 to 4) and propylene-based glycol ether
represented by CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1
to 4, y=an integer of 1 to 3).
[0040] First, the following will describe the glycol ether used in
the present invention. The glycol ether is one of the organic
solvents, and has been used, for example, as a solvent for paint or
ink. The glycol ether may include, for example, the ethylene glycol
type (E.O. type) based on ethylene glycol, the propylene glycol
type (P.O. type) based on propylene glycol, and other types. The
present inventors have found that in the glycol ethers of the E.O.
type and the P.O. type, particularly when the ethylene-based glycol
ether represented by the following formula (1) and the
propylene-based glycol ether represented by the following formula
(2) are used in combination with a reducing agent, the effect as a
removal treatment agent (filler removal treatment agent) such as a
silica-based filler is further enhanced, so that adhesion between
an insulating resin substrate and a plating film is remarkably
improved. The reason why the adhesion is improved by using the
glycol ether is, for example, that the filler exposed on the resin
surface after roughening treatment is efficiently removed by the
mechanism described above. Further, it is presumed that it is one
factor improving the adhesion is that, after the roughening
treatment, treatment is carried out with a reducing agent and a
pretreating liquid containing the above-described glycol ether to
swell the resin around the filler, so that the plating film tends
to precipitate between the filler and the resin.
CmH(2m+1)-(OC.sub.2H.sub.4)n-OH (m=an integer of 1 to 4,n=an
integer of 1 to 4) (1)
CxH(2x+1)-(OC.sub.3H.sub.6)y-OH (x=an integer of 1 to 4,y=an
integer of 1 to 3) (2)
[0041] Thus, the present invention is one having technical
significance in that the glycol ethers represented by the formulas
(1) and (2), in particular, among other glycol ethers act as good
filler removing agents when used simultaneously with a reducing
agent.
[0042] As in the present invention, Patent Document 1 also
discloses a pretreating liquid to be used simultaneously with the
reducing agent; however, in Patent Document 1, a fluorine compound
is used as a filler removing agent at the time of reduction, and in
this point, Patent Document 1 is different from the present
invention using the above-described glycol ether as the filler
removing agent at the time of reduction. When the glycol ether is
used as in the present invention, the filler removing effect is
more effectively exhibited as compared with the case where a
fluorine compound is used, and as a result, the adhesion to the
plating film is further improved. This point is also demonstrated
in the column of examples to be described below, and peel strength
as an index of adhesion was lowered in Test No. 22 in Table 1 using
a fluorine compound instead of glycol ether.
[0043] As the ethylene-based glycol ether represented by the
formula (1), there can be mentioned ethylene glycol methyl ether
(n=1, m=1), ethylene glycol ethyl ether (n=1, m=2), ethylene glycol
propyl ether (n=1, m=3), ethylene glycol butyl ether (n=1, m=4),
diethylene glycol methyl ether (n=2, m=1), diethylene glycol ethyl
ether (n=2, m=2), diethylene glycol propyl ether (n=2, m=3),
diethylene glycol butyl ether (n=2, m=4), triethylene glycol methyl
ether (n=3, m=1), triethylene glycol ethyl ether (n=3, m=2),
triethylene glycol propyl ether (n=3, m=3), triethylene glycol
butyl ether (n=3, m=4), tetraethylene glycol methyl ether
(n=4,m=1), tetraethylene glycol ethyl ether (n=4, m=2),
tetraethylene glycol propyl ether (n=4, m=3), and tetraethylene
glycol butyl ether (n=4, m=4).
[0044] As the propylene-based glycol ether represented by the
formula (2), there can be mentioned propylene glycol methyl ether
(x=1, y=1), dipropylene glycol methyl ether (x=1, y=2),
tripropylene glycol methyl ether (x=1, y=3), propylene glycol ethyl
ether (x=2, y=1), dipropylene glycol ethyl ether (x=2, y=2),
tripropylene glycol ethyl ether (x=2, y=3), propylene glycol propyl
ether (x=3, y=1), dipropylene glycol propyl ether (x=3, y=2),
tripropylene glycol propyl ether (x=3, y=3) propylene glycol butyl
ether (x=4, y=1), dipropylene glycol butyl ether (x=4, y=2), and
tripropylene glycol butyl ether (x=4, y=3).
[0045] The propyl and butyl in the glycol ethers represented by the
formulas (1) and (2) may have a linear or branched chain
structure.
[0046] Taking into consideration, for example, a further
enhancement in adhesion, the glycol ether may preferably be
ethylene-based glycol ethers represented by the formula (1), more
preferably diethylene glycol butyl ethers (such as diethylene
glycol mono-n-butyl ethers).
[0047] In the present invention, the glycol ethers represented by
the formulas (1) and (2) may be used alone or in combination. As
examples of combined use, there can be mentioned examples of using
two or more glycol ethers represented by the formula (1), examples
of using two or more glycol ethers represented by the formula (2),
and examples of using at least one glycol ether represented by the
formula (1) and at least one glycol ether represented by the
formula (2).
[0048] The pretreating liquid of the present invention contains the
above-described glycol ether and a reducing agent. The reducing
agent used in the present invention is not particularly limited as
long as it is a reducing agent usually used in reduction treatment
after roughening treatment, and examples of the reducing agent
include hydrogen peroxide, hydroxylammonium sulfate, glyoxylic
acid, and various amine-based compounds such as hydroxylamine
sulfate, ethylenediamine, diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, monoethanolamine, diethanolamine,
ethylenediaminetetraacetic acid, and nitrilotriacetic acid.
[0049] The pH of the pretreating liquid according to the present
invention is approximately 3.0 or less. As a result, the action of
the reducing agent is effectively exhibited.
[0050] Here, if the total amount of the glycol ether, reducing
agent, and water is defined as the "whole amount of pretreating
liquid", the amount of the glycol ether contained in the
pretreating liquid (this amount means the amount of only one glycol
ether contained, when the only one glycol ether is contained in the
pretreating liquid, or the total amount of two or more glycol
ethers contained, when the two or more glycol ethers are contained
in the pretreating liquid) may be preferably 30 g/L or more and 800
g/L or less, more preferably 50 g/L or more and 600 g/L or less,
relative to the whole amount of pretreating liquid. When the amount
of glycol ether is smaller than the above lower limit, the addition
effect of glycol ether is not effectively exhibited, thereby lowing
plating adhesion. On the other hand, even if glycol ether is added
beyond the above upper limit, the addition effect of glycol ether
is saturated, thereby becoming wasteful from an economical point of
view.
[0051] The amount of the reducing agent contained in the
pretreating liquid may be preferably 0.1 g/L or more and 500 g/L or
less, more preferably 1 g/L or more and 300 g/L or less, relative
to the whole amount of pretreating liquid. When the amount of the
reducing agent is smaller than the above lower limit, the addition
effect of the reducing agent is not effectively exhibited, thereby
lowing removal performance for manganese adsorbed to the substrate.
On the other hand, even if the reducing agent is added beyond the
above upper limit, the addition effect of the reducing agent is
saturated, thereby becoming wasteful from an economical point of
view.
[0052] The pretreating liquid of the present invention contains a
reducing agent and the above-described glycol ether and may further
contain other components used for reduction treatment as long as
the pH of the pretreating liquid satisfies the above range.
[0053] For example, the pretreating liquid may further contain a
fluorine compound. The addition of the fluorine compound further
improves the adhesion. As the fluorine compound to be used in the
present invention, there can be mentioned, for example, acidic
sodium fluoride, acidic ammonium fluoride, ammonium hydrogen
difluoride as disclosed in JP-A-2010-106337, and fluorine compounds
as disclosed in Patent Document 1 above (e.g., hydrogen fluoride;
fluoroboric acid; sodium salts such as sodium fluoride and sodium
hydrogen fluoride; and ammonium salts such as ammonium hydrogen
fluoride, ammonium hexafluorosilicate, and ammonium
hexafluorophosphate). These fluorine compounds may be added alone,
or two or more of them may be used in combination.
[0054] The fluorine compound is useful for the enhancement of
adhesion strength between an insulating resin substrate and a
plating film. The fluorine compound preferably used in the present
invention is acidic sodium fluoride or acidic ammonium fluoride, in
which more preferred is acidic ammonium fluoride.
[0055] The amount of fluorine compound contained in the pretreating
liquid (this amount means the amount of only one fluorine compound
contained, when the only one fluorine compound is contained in the
pretreating liquid, or the total amount of two or more fluorine
compounds contained, when the two or more fluorine compounds are
contained in the pretreating liquid) may be preferably 0.01 g/L or
more and 100 g/L or less, more preferably 1 g/L or more and 50 g/L
or less, relative to the total amount of pretreating liquid. When
the amount of fluorine compound is below the lower limit, the
addition effect of fluorine compound is not effectively exhibited,
resulting in the lowering of adhesion strength. On the other hand,
even if the fluorine compound is added beyond the above upper
limit, the addition effect of the fluorine compound is saturated,
thereby becoming wasteful from an economical point of view.
[0056] The pretreating liquid may further contain a surfactant,
whereby permeability and the like are improved. The type of the
surfactant is not particularly limited, but non-ionic surfactants
and ionic surfactants can be used. These fluorine compounds may be
added alone, or two or more of them may be used in combination.
[0057] The non-ionic surfactants are useful as the surface tension
reducing agent of the pretreating agent. When a cationic surfactant
is used as an additional surfactant, the non-ionic surfactant
further exhibits the action as a dispersant of the cationic
surfactant. Preferred examples of the non-ionic surfactant may
include polyoxyethylene alkyl ether; and polyoxyethylene alkyl
phenyl ethers such as polyoxyethylene octyl phenyl ether and
polyoxyethylene nonyl phenyl ether. These non-ionic surfactants may
be added alone, or two or more of them may be used in
combination.
[0058] Further, the ionic surfactants include cationic surfactants,
anionic surfactants, and ampholytic surfactants, all of which can
be used in the present invention.
[0059] Among these, the cationic surfactants have the action of
neutralizing electric charges by being adsorbed onto the surface of
a negatively charged insulating resin substrate. Preferred cationic
surfactants are poly(diallyl dimethyl ammonium chloride),
copolymers of poly(diallyl dimethyl ammonium chloride) and
acrylamide, and polyethyleneimine.
[0060] The anionic surfactants have the action of neutralizing
electric charges by being adsorbed onto the surface of a positively
charged insulating resin substrate. As the anionic surfactant,
those disclosed in JP-A-2011-228517 can be used.
[0061] The ampholytic surfactants show the nature of anionic
surfactants in an alkaline region and the nature of cationic
surfactants in an acidic region. As described below, the
pretreating liquid of the present invention may preferably indicate
acidity of pH 3.1 or less, and therefore, it exhibits the nature of
cationic surfactants by the use of ampholytic surfactants. As the
ampholytic surfactants, those disclosed in JP-A-2011-228517 can be
used.
[0062] In the present invention, the amount of the surfactant
contained in the pretreatment agent (when only one surfactant is
contained, it means the amount of this surfactant, or when two or
more surfactants are contained, it means the total amount of these
surfactants) may be preferably 0.1 g/L or more and 500 g/L or less,
more preferably 1 g/L or more and 100 g/L or less, relative to the
whole amount of pretreatment agent. When the amount of surfactant
is below the above lower limit, the addition effect of surfactant
is not effectively exhibited, deteriorating the precipitation
properties of an electroless Cu plating film onto a glass. On the
other hand, even if a surfactant is added beyond the above upper
limit, the addition effect of surfactant is saturated, becoming
wasteful from an economical point of view.
[0063] The foregoing has described in detail the components
constituting the pretreating liquid of the present invention.
[0064] The following will describe a process for producing a
printed wiring board according to the present invention. The
production process of the present invention includes a roughening
treatment step of roughening an insulating resin substrate
containing a filler, a reduction and filler removal step of
reducing residues generated on the insulating resin substrate by
the roughening treatment step and, at the same time, removing the
filler contained in the resin insulating substrate, and an
electroless plating step of applying electroless plating to an
insulating resin etched in the reduction and filler removal step.
In this production process, the pretreating liquid of the present
invention described above is used in the reduction and filler
removal step. Since the production process of the present invention
uses the pretreating liquid of the present invention described
above, a printed wiring board having extremely excellent adhesion
between the filler-containing insulating resin substrate and the
plating film can be obtained.
[0065] The following will describe each step.
[0066] First, an insulating resin substrate containing a filler is
prepared. The insulating resin to be used in the present invention
is not particularly limited, so long as it is a resin usually used
in desmear treatment and the like, and as such an insulating resin,
the following resins can be mentioned, in addition to epoxy resins
widely used as electrically insulating resins, imide resins, phenol
formaldehyde resins, novolac resins, melamine resins, polyphenylene
ether resins, bismaleimide-triazine resins, siloxane resins,
maleimide resins, polyether ether ketone resins, polyether imide
resins, and polyether sulfone resins. Needless to say, the present
invention is not limited thereto. In addition to the above resins,
it is also possible to use, for example, a resin produced by mixing
two or more kinds of resins selected from the above-described
resins at an arbitrary ratio.
[0067] Typical examples of the filler used in the present invention
include a silica-based filler. The silica-based filler is useful
for improving the mechanical and electrical characteristics and the
like of the insulating resin substrate and also contributes to
improvement in adhesion between the insulating resin substrate and
the plating film due to the anchor effect during roughening
treatment.
[0068] Excellent plating adhesion by the pretreating liquid of the
present invention is effectively exhibited even when the amount of
SiO.sub.2 contained in the insulating resin is, for example, 30% by
mass or more (further, for example, 40% by mass or more and 95% by
mass or less) and, that is, the amount of SiO.sub.2 contained in
the insulating resin is large as compared with a usual silica-based
filler.
[0069] Further, the excellent plating adhesion by the pretreating
liquid of the present invention is effectively exhibited even when
surface roughness (Ra) of the filler-containing insulating resin
substrate is as small as approximately 0.01 to 0.1 .mu.m.
[0070] Then, the filler-containing insulating resin substrate is
swollen. By swelling treatment, the substrate surface is easily
roughened in roughening treatment in the subsequent step. As a
swelling liquid used in the swelling treatment, there can be
mentioned, for example, N-methyl-2-pyrrolidone,
N,N-dimethylacetamide, N,N-dimethyl formamide,
.gamma.-butyrolactone, and ethylene glycol monobutyl ether. The
swelling treatment is preferably carried out by immersing the
filler-containing insulating resin substrate in the swelling liquid
at a temperature of about 60 to 90.degree. C. for 10 to 30
minutes.
[0071] Then, the filler-containing insulating resin substrate
subjected to the swelling treatment is washed with water, and then,
the substrate surface is roughened (etched). As the etchant used
for the roughening treatment, there can be mentioned aqueous sodium
permanganate solution, aqueous potassium permanganate solution,
aqueous sodium chromate solution, and aqueous potassium chromate
solution. The roughening treatment is carried out by bringing the
filler-containing insulating resin substrate washed with water into
contact with an alkali solution of the above-described etchant. As
the contact method, immersion and the like can be mentioned.
Specifically, it is preferable that the filler-containing
insulating resin substrate is brought into contact at a temperature
of about 50 to 80.degree. C. for 1 to 10 minutes, for example, to
roughen the resin surface.
[0072] After the surface of the resin substrate is thus roughened,
reduction and filler removal are carried out using the pretreating
liquid of the present invention. Specifically, filler removal
treatment using the above-described glycol ether is carried out at
the same time as dissolution treatment (reduction treatment)
according to reduction reaction for treatment residues such as
manganese oxide generated on the resin substrate surface by
roughening treatment.
[0073] It is preferable that the above-described reduction and
filler removal is carried out, for example, by immersing the
roughened filler-containing insulating resin substrate in the
pretreating liquid of the present invention and carrying out
treatment at a temperature of about 20 to 80.degree. C. for about 5
seconds to 10 minutes. As a result, not only dissolution and
removal of roughening residues such as manganese oxide but also
filler removal are carried out.
[0074] Then, if necessary, ultrasonic treatment may be carried out,
whereby the filler removing effect is enhanced, and the adhesion is
further improved. As ultrasonic treatment conditions, for example,
it is preferable to control the frequency within a range of 20 to
200 kHz. It is more preferable to control the frequency within a
range of 24 to 100 kHz. When the frequency is below the above lower
limit, the above effect is not effectively exhibited. On the other
hand, when the frequency is beyond the upper limit, damage to the
substrate becomes large. In addition, it is preferable to control
an ultrasonic irradiation time within a range of approximately 10
seconds to 10 minutes. When the irradiation time is less than 10
seconds, the above effect is not effectively exhibited. On the
other hand, if the irradiation time exceeds 10 minutes, excessive
etching may occur with respect to the inner layer metal.
[0075] Then, the resin substrate is cleaned by cleaning treatment
using a well-known method. This cleaning treatment removes dirt and
the like from the resin substrate surface to clean the surface and,
at the same time, imparts water-wettability to the resin substrate,
so that the adhesion to the plating film to be formed in the
subsequent step is further improved. The type of the solution used
for this cleaning treatment is not particularly limited, and, for
example, a cleaner/conditioner containing at least both a nonionic
surfactant and a cationic surfactant is used. Specifically, it is
preferable to immerse the above-described surface-treated resin
substrate in a cleaner/conditioner at about 40.degree. C. for 5
minutes.
[0076] After plating pretreatment is carried out as described
above, plating treatment is carried out. The method of the plating
treatment is not particularly limited, and a plating film is formed
by adopting a commonly used method such as a semi additive method
or a full additive method. For details of the plating treatment,
reference can be made, for example, to Patent Document 1 described
above and the description in JP-A-2015-71821.
[0077] Hereinafter, a plating treatment method according to the
full additive method will be described in detail. In the following
example, although a copper plating film is formed, the type of the
plating film is not limited to the copper plating film but may be
another metal plating film such as a nickel plating film. Instead
of the plating treatment according to the full additive method, a
plating film may be formed by electroplating using a semi additive
method.
[0078] After the swelling treatment and the roughening treatment
described above, reductive dissolution treatment and the filler
removal are treated on treatment residues, generated by the
roughening treatment, using the pretreating liquid of the present
invention.
[0079] Then, a catalyst is applied to the resin substrate surface
on which a circuit pattern is to be formed. The type of the
catalyst used for the catalyst application is not particularly
limited as long as the catalyst is commonly used, and, for example,
a catalyst solution containing divalent palladium ions (Pd.sup.2+),
a mixed solution containing palladium chloride
(PdCl.sub.2-2H.sub.2O), stannous chloride (SnCl.sub.2-2H.sub.2O),
and hydrochloric acid (HCl), or the like can be used. For example,
it is preferable that the mixed solution have a concentration of,
for example, 100 to 300 mg/L as the Pd concentration, 10 to 20 g/L
as the Sn concentration, and 150 to 250 mL/L as the HCl
concentration. The insulating resin substrate is immersed in such a
catalyst solution at a temperature of 30 to 40.degree. C. for 1 to
3 minutes, for example, to first make a Pd--Sn colloid adsorbed on
the resin substrate surface. Then, the insulating resin substrate
is immersed in an accelerator (promotor) comprising 50 to 100 mL/L
of sulfuric acid or hydrochloric acid, for example, under normal
temperature conditions to activate the catalyst. Tin is removed
from a complex compound by this catalyst activation treatment to
provide palladium adsorption particles, which finally serves as a
palladium catalyst to promote the subsequent copper deposition by
electroless copper plating. Sodium hydroxide or an ammonia solution
may be used as the accelerator. When the catalyst is applied to the
resin substrate, pretreatment using a conditioner solution or a
pre-dipping solution may be carried out to further enhance the
adhesion between the resin substrate and the copper plating film,
and furthermore, pretreatment for improving the wettability of the
catalyst onto the resin substrate surface may be carried out.
[0080] Then, after the catalyst is applied to the insulating resin
substrate in this way, if necessary, a plating resist for forming a
desired circuit pattern is formed. That is, a resist pattern
masking other portions than a part to be deposited with a copper
plating film constituting a circuit pattern in the next step is
formed. The resist pattern may be peeled and removed, after
termination of plating treatment, by etching operation or the like,
or the resist pattern may function as a solder resist without being
peeled and removed after plating treatment. The method of forming a
plating resist can be carried out using well-known methods.
[0081] After the plating resist is formed, a copper plating film is
deposited by an electroless plating method to form a circuit
pattern. When the copper plating film is to be deposited by the
electroless plating method, after the formation of the plating
resist, by using 10% sulfuric acid and reducer, for example,
palladium adsorption particles of the catalyst adhered on the resin
substrate surface are reduced to activate the catalyst, and
deposition of copper plating on the resin substrate may be
improved.
[0082] Specifically, as a plating bath used for the electroless
copper plating, for example, a plating bath containing EDTA as a
complexing agent can be used. As one example of the composition of
the electroless copper plating bath described above, it is possible
to use an electroless copper plating bath containing copper sulfate
(10 g/L) and EDTA (30 g/L) and being adjusted to a pH of about 12.5
with sodium hydroxide. Alternatively, an electroless copper plating
bath using Rochelle salt as a complexing agent may be used. The
insulating resin substrate is immersed in this electroless copper
plating bath at a temperature of 60 to 80.degree. C. for 30 to 600
minutes, for example, to form a copper plating film. For example,
when a via or the like for electrical conduction with a lower layer
is formed in a multilayer wiring board, it is preferable to
sufficiently stir the liquid so that ions are sufficiently supplied
to the via. The stirring method is not particularly limited, but
there can be used, for example, air stirring or any other stirring
such as pump circulation.
[0083] In the plating treatment, two-step plating may be carried
out to further enhance the adhesion to the insulating resin
substrate. That is, primary plating treatment to form an underlying
plating film on a resin substrate is carried out, and secondary
plating treatment to form a thick plating film, of which thickness
becomes thicker than the underlying plating film, on the formed
underlying plating film may be carried out to form a circuit
pattern. Particularly in the primary plating treatment, the
internal stress has a direction different from the direction of the
internal stress of the thick plating film formed by the secondary
plating treatment; in other words, the internal stress has a
direction opposite to the direction of the internal stress of the
thick plating film formed by the secondary plating treatment, and
plating treatment may be generally carried out using an electroless
plating bath for forming an underlying plating film having tensile
internal stress.
[0084] This application claims the benefit of priority to Japanese
Patent Application No. 2016-158009, filed on Aug. 10, 2016. The
entire contents of the specifications of Japanese Patent
Application No. 2016-158009, filed on Aug. 10, 2016 are
incorporated herein by reference.
EXAMPLES
[0085] Next, the present invention will be described more
concretely by way of Examples and Comparative Examples. However,
the present invention is by no means limited by modes of the
Examples, and may appropriately be modified within a range not
deviated from the gist of the present invention.
Example 1
[0086] In this example, the following samples were prepared using a
pretreating liquid containing the components listed in Table 1. In
Table 1, the fluorine compound means acidic ammonium fluoride
(available from Kishida Chemical Co., Ltd.). The fluorine compound
had a concentration of 5 g/L in all cases. On the other hand, a
reducing agent had a concentration of 20 g/L in all cases.
[0087] Specifically, first, insulating resin substrates each having
a glass epoxy substrate (FR-4 as the NEMA symbol) and a resin film
ABF-GX92R (containing in the insulating resin substrate 45% by mass
of a silica-based filler in terms of SiO.sub.2) available from
Ajinomoto Fine-Techno Co., Inc. layered on the glass epoxy
substrate were swollen and roughened in the procedures as shown in
Table 2, treated with various pretreating liquids as shown in Table
1, and if necessary, subjected to ultrasonic treatment (frequency:
28 KHz), dried, and treated with a cleaner/conditioner. The surface
roughness Ra at this time was 0.18 .mu.m. Then, the insulating
resin substrates were softly etched, pickled, and provided with a
Pd catalyst by the catalyst imparting process (predip, activator,
reducer, and accelerator), followed by electroless copper plating
and drying to form a plating film of 0.8 .mu.m in thickness.
Further, the plated substrates were dried, heat treated, cleaned,
and pickled, followed by electrolytic copper plating under the
condition of 2.5 A/dm.sup.2 to form a copper plating film of 25
.mu.m in thickness. The plated substrates were then subjected to
discoloration preventive treatment, drying, and heat treatment to
prepare the samples.
[0088] The samples thus prepared were measured for adhesion
strength between a plating film and an insulating resin substrate
as follows.
[0089] (Measurement of Adhesion Strength Between Plating Film and
Insulating Resin Substrate)
[0090] A cut of 1 cm in width was made in each of the above
samples, followed by 90.degree. peel test according to the method
as described in JIS-C5012, "8.5 Plating Adhesion", to measure peel
strength with Autograph AGS-X Series Precision Universal Tester
available from Shimadzu Corporation.
[0091] The results are shown in Table 1.
[0092] For reference, surface SEM photographs of Test No. 19
(Comparative Example) and Test No. 5 (Working Example) in Table 1
are shown.
TABLE-US-00001 TABLE 1 Pretreatment solution Ultrasonic Evaluation
Test Fluorine treatment after Adhesion No. Classification Type
Concentration compound Reducing agent pretreatment Peel strength 1
Ethylene glycol Ethylene glycol 200 g/L Not contained hydrogen
peroxide Presence 640 gf/cm types mono-n-butyl ether 2 Diethylene
glycol 200 g/L Not contained hydrogen peroxide Presence 675 gf/cm
mono-n-butyl ether 3 Diethylene glycol 100 g/L Not contained
hydrogen peroxide Presence 670 gf/cm mono-n-butyl ether 4
Diethylene glycol 300 g/L Not contained hydrogen peroxide Presence
680 gf/cm mono-n-butyl ether 5 Diethylene glycol 200 g/L Contained
hydrogen peroxide Presence 705 gf/cm mono-n-butyl ether 6
Diethylene glycol 200 g/L Not contained hydroxylammonium Presence
680 gf/cm mono-n-butyl ether sulfate 7 Diethylene glycol 200 g/L
Not contained glycocylic acid Presence 685 gf/cm mono-n-butyl ether
8 Triethylene glycol 200 g/L Not contained hydrogen peroxide
Presence 670 gf/cm mono-n-butyl ether 9 Tetraethylene glycol 200
g/L Not contained hydrogen peroxide Presence 648 gf/cm monomethyl
ether 10 Diethylene glycol 200 g/L Not contained hydrogen peroxide
Absence 605 gf/cm mono-n-butyl ether 11 Ethylene glycol 200 g/L Not
contained hydrogen peroxide Presence 643 gf/cm monomethyl ether 12
Triethylene glycol 200 g/L Not contained hydrogen peroxide Presence
623 gf/cm mono-ethyl ether 13 Ethylene glycol 200 g/L Not contained
hydrogen peroxide Presence 636 gf/cm monopropyl ether 14 Propylene
glycol Propylene glycol 200 g/L Not contained hydrogen peroxide
Presence 675 gf/cm types mono-methyl ether 15 Propylene glycol 200
g/L Not contained hydrogen peroxide Presence 645 gf/cm mono-ethyl
ether 16 Propylene glycol 200 g/L Not contained hydrogen peroxide
Presence 639 gf/cm mono-propyl ether 17 Dipropylene glycol 200 g/L
Not contained hydrogen peroxide Presence 671 gf/cm monomethyl ether
18 Tripropylene glycol 200 g/L Not contained hydrogen peroxide
Presence 664 gf/cm monomethyl ether 19 -- -- Not contained hydrogen
peroxide Presence 420 gf/cm 20 Ethylene glycol Diethylene glycol 10
g/L Not contained hydrogen peroxide Presence 485 gf/cm types
mono-n-butyl ether 21 N-methyl-2-pyrrolidone 100 g/L Not contained
hydrogen peroxide Presence 449 gf/cm 22 -- -- Contained hydrogen
peroxide Presence 510 gf/cm
TABLE-US-00002 TABLE 2 Treatment Treatment temperature time Steps
Name of chemicals Concentration (.degree. C.) (min.) Swelling
APPDES MDS-37 500 mL/L 70 10 available from C. Uyemura & Co.,
Ltd. Roughening MDE-40 100 mL/L 80 15 available from C. Uyemura
& Co., Ltd. ELC-SH 140 mL/L available from C. Uyemura &
Co., Ltd. Neutralization See Table 1 60 5 (Pretreatment) Ultrasonic
treatment 25 5 Drying Cleaner/Conditioner SULCUP MCD-PL 50 mL/L 40
5 available from C. Uyemura & Co., Ltd. Soft etching Sodium
persulfate 100 g/L 25 1 Sulfuric acid 100 g/L Pickling Sulfuric
acid 100 g/L 25 1 Catalyst Predip ALCUP MDP-2 10 mL/L 25 2
imparting available from C. Uyemura & Co., Ltd. Sulfuric acid 3
g/L Activator ALCUP MAT-SP 50 mL/L 40 5 available from C. Uyemura
& Co., Ltd. 1N--NaOH 40 mL/L Reducer ALCUP MAB-4-A 10 mL/L 35 3
available from C. Uyemura & Co., Ltd. ALCUP MAB-4-C 50 mL/L
available from C. Uyemura & Co., Ltd. ALCUP MRD-2-C 10 mL/L
available from C. Uyemura & Co., Ltd. Accelerator THRU-CUP
MEL-3-A 50 mL/L 25 1 available from C. Uyemura & Co., Ltd.
Electroless copper plating THRU-CUP PEA-6-A 100 mL/L 36 15
available from C. Uyemura & Co., Ltd. THRU-CUP PEA-6-B-2X 50
mL/L available from C. Uyemura & Co., Ltd. THRU-CUP PEA-6-C 14
mL/L available from C. Uyemura & Co., Ltd. THRU-CUP PEA-6-D 15
mL/L available from C. Uyemura & Co., Ltd. THRU-CUP PEA-6-E 50
mL/L available from C. Uyemura & Co., Ltd. Drying Heat
treatment 150 30 Cleaner THRU-CUP MSC-3-A 100 mL/L 40 5 available
from C. Uyemura & Co., Ltd. Pickling Sulfuric acid 100 g/L 25 1
Electrolytic copper plating THRU-CUP ETN (2.5 A/dm.sup.2) 25 45 (25
.mu.m) available from C. Uyemura & Co., Ltd. Decoloration
prevention THRU-CUP AT-21 1 mL/L 25 1 available from C. Uyemura
& Co., Ltd. Drying Heat treatment 190 60
[0093] The following discussion can be made from Table 1.
[0094] First, Test Nos. 1 to 18 are Working Examples using the
pretreating liquid of the present invention. In all the cases of
ethylene-based glycol types (Nos. 1 to 13) or propylene-based
glycol types (Nos. 14 to 18), the peel strength was 600 gf/cm or
more, and samples excellent in adhesion to a plating film were
obtained. In detail, Test Nos. 2, 5 to 7, and 10 are examples in
which diethylene glycol mono-n-butyl ether (n=2, m=4) was used at a
concentration of 200 g/L, and good adhesion was obtained regardless
of the type of the reducing agent. When ultrasonic treatment was
carried out after the treatment with the pretreating liquid, the
above effect was further improved as compared with Test No. 10
which was not subjected to ultrasonic treatment. Among the above
examples subjected to ultrasonic treatment, in Test No. 5 further
added with a fluorine compound, the adhesion was further improved,
and the peel strength exceeded 700 gf/cm.
[0095] Test No. 20 is a reference example in which the
concentration of glycol ether in ethylene glycol is low, and the
adhesion was lowered.
[0096] On the other hand, Test Nos. 19, 21, and 22 are comparative
examples of each using a pretreating liquid failing to fulfill any
of the requirements of the present invention. These comparative
examples had the following problems.
[0097] No. 19 was a comparative example containing only the
reducing agent and not containing the glycol ether specified in the
present invention, and the adhesion was lowered because the filler
removing effect at the time of reduction was insufficient.
[0098] Test No. 21 is a comparative example using not the
pretreating liquid of the present invention but a treating liquid
containing N-methyl-2-pyrrolidone, which was commonly used for
swelling treatment, and a reducing agent, the filler removing
effect at the time of reduction was not effectively exhibited, and
the adhesion was lowered.
[0099] Test No. 22 is a comparative example simulating Patent
Document 1 and is an example using a fluorine compound instead of
the glycol ether specified in the present invention. Although the
addition of the fluorine compound improved the peeling strength of
Test No. 22 as compared with Test Nos. 19 and 21 as Comparative
Examples, it is understood that the peel strength of Test No. 22
was inferior to that of Test Nos. 1 to 18 as Working Examples.
[0100] Further, from FIG. 1, it is understood that the pretreating
liquid of the present invention is excellent in the filler removing
effect at the time of reduction. In detail, in Test No. 19 as
Comparative Example, as shown in FIG. 1 (a), a large amount of
filler (indicated by an arrow in the FIGURE) which was not removed
remained on the surface, whereas in Test No. 5 as Working Example,
almost no filler was observed as shown in FIG. 1 (b).
[0101] These results have demonstrated that in order to ensure
desired adhesion, it is useful to use a reducing agent and a
treating liquid containing the glycol ether specified in the
present invention.
* * * * *